IsMySiteUp.com
Worried about downtime on your Web site? An excellent free service,
IsMySiteUp.com constantly monitors your Web site and alerts you (via E-mail or
pager) if your server encounters downtime. IsMySiteUp.com is easy to use and a
snap to set up.

SiteProbe
This handy freeware online tool checks the status of your site hourly, 24
hours a day. It also offers a helpful "second opinion" system to reduce the
number of potential false alarms.

InternetSeer
This service monitors your Web site around the clock and alerts you via E-mail
if your site encounters downtime and becomes inaccessible. InternetSeer's
basic "Standard Service" is free and allows you the monitoring of one URL per
hour. (Note: currently, this service won't work with
WebTV URLs).

LinkCounter.com(This service is no longer free). Have you ever
wondered how many clicks your site is sending to an affiliate program or
linkback partner? This unique service monitors the number of clicks your links
are getting. It also monitors internal links so you'll know where your
visitors are going.